After reading the "Wanted Fresh Fish" mission page, I was rolling around this thought. From what ive seen, only grenades and explosive elemental weapons will activate the markers and release the fish for collecting, Yes? If so, i often found myself useing a Volcano for this task since they are so fairly common. It would sometimes take several hits to cause the release but it does work. I dont recall any other type of damage causing the release.
Now my thought is, if the above explosive situation during the mission is true, does this mean that the Volcano has some kind of hidden explosive damage as well as the fire damage that would account for the large proc cloud seen during use. This would coincide with the fact that volcanic eruptions can be quite explosive.
With the recent (albeit unconfirmed) addition to the "Wanted: Fresh Fish" page, stating that Lilith's Phase Blast can even trigger the effect, I would not be surprised if any AoE damage or splash damage triggered the release of the fish. It would be interesting to test. 05:04, November 20, 2011 (UTC)